The conventional art includes optical devices for data reception and transmission, such as used for optical inter-chip interconnects and the like. For example, Vertical Cavity Surface Emitting Lasers (VCSELs) are used for optical interconnects due to their performance (high-modulation bandwidth, low power consumption, high efficiency) and manufacturing advantages (high-volume production, wafer-level testing, and ease of integration). The low power requirements of these VCSELs allow simple electronic driver circuits to be used. VCSELs are generally about hundreds of microns in size.
Conventional art also includes electrical devices, such as signal manipulation devices (e.g., switches and cross-connects) or data processing devices (e.g., mathematical processors or DSP). Current technologies, such as Complementary Metal Oxide Semiconductor (CMOS) technology, produce devices that are on the order of tens of nanometers in size.
Usually, connections are provided between these optical and electrical devices, using serializers and deserializers, which work at high frequency (high bit rate).
However, these combined solutions have various disadvantages, such as high energy consumption and large size, and the devices which incorporate them have a large number of components and, consequently, are very complex systems, which can also result in possible problems of reliability. Thermal stability and limitations of possible achieved high bit rate are well known issues with such approaches.
Moreover, there are technology difficulties which prevent integration of optical devices and processing systems on the same silicon microchip, so that devices which incorporate them are usually formed of at least two distinct and physically separate elements, the electro-optical part and the processor or switch units for manipulating the data acquired.
For example, in order to modulate light from optical sources, such as VCSELS, and to receive the signals with high bit rate, high speed electronic circuitry is needed. In order to achieve these high frequencies and high bit rate signals, such electronic circuitry has been built using SiGe materials. This means that, in order to build an integrated device, three layers of different materials must be connected—CMOS for the logic or processing device, an SiGe layer, to build high speed driving/receiving electronic modules and finally, a GaAs and/or InP layer for the optoelectronic devices. Thus, it is very difficult to construct such an integrated device.
Generally, the conventional art utilizes a combination of different devices, with some devices that combine one or more functions, albeit with an incomplete level of integration.